69 lines
2.9 KiB
Plaintext
69 lines
2.9 KiB
Plaintext
|
spi_butterfly - parport-to-butterfly adapter driver
|
||
|
|
===================================================
|
||
|
|
|
||
|
|
This is a hardware and software project that includes building and using
|
||
|
|
a parallel port adapter cable, together with an "AVR Butterfly" to run
|
||
|
|
firmware for user interfacing and/or sensors. A Butterfly is a $US20
|
||
|
|
battery powered card with an AVR microcontroller and lots of goodies:
|
||
|
|
sensors, LCD, flash, toggle stick, and more. You can use AVR-GCC to
|
||
|
|
develop firmware for this, and flash it using this adapter cable.
|
||
|
|
|
||
|
|
You can make this adapter from an old printer cable and solder things
|
||
|
|
directly to the Butterfly. Or (if you have the parts and skills) you
|
||
|
|
can come up with something fancier, providing ciruit protection to the
|
||
|
|
Butterfly and the printer port, or with a better power supply than two
|
||
|
|
signal pins from the printer port. Or for that matter, you can use
|
||
|
|
similar cables to talk to many AVR boards, even a breadboard.
|
||
|
|
|
||
|
|
This is more powerful than "ISP programming" cables since it lets kernel
|
||
|
|
SPI protocol drivers interact with the AVR, and could even let the AVR
|
||
|
|
issue interrupts to them. Later, your protocol driver should work
|
||
|
|
easily with a "real SPI controller", instead of this bitbanger.
|
||
|
|
|
||
|
|
|
||
|
|
The first cable connections will hook Linux up to one SPI bus, with the
|
||
|
|
AVR and a DataFlash chip; and to the AVR reset line. This is all you
|
||
|
|
need to reflash the firmware, and the pins are the standard Atmel "ISP"
|
||
|
|
connector pins (used also on non-Butterfly AVR boards). On the parport
|
||
|
|
side this is like "sp12" programming cables.
|
||
|
|
|
||
|
|
Signal Butterfly Parport (DB-25)
|
||
|
|
------ --------- ---------------
|
||
|
|
SCK = J403.PB1/SCK = pin 2/D0
|
||
|
|
RESET = J403.nRST = pin 3/D1
|
||
|
|
VCC = J403.VCC_EXT = pin 8/D6
|
||
|
|
MOSI = J403.PB2/MOSI = pin 9/D7
|
||
|
|
MISO = J403.PB3/MISO = pin 11/S7,nBUSY
|
||
|
|
GND = J403.GND = pin 23/GND
|
||
|
|
|
||
|
|
Then to let Linux master that bus to talk to the DataFlash chip, you must
|
||
|
|
(a) flash new firmware that disables SPI (set PRR.2, and disable pullups
|
||
|
|
by clearing PORTB.[0-3]); (b) configure the mtd_dataflash driver; and
|
||
|
|
(c) cable in the chipselect.
|
||
|
|
|
||
|
|
Signal Butterfly Parport (DB-25)
|
||
|
|
------ --------- ---------------
|
||
|
|
VCC = J400.VCC_EXT = pin 7/D5
|
||
|
|
SELECT = J400.PB0/nSS = pin 17/C3,nSELECT
|
||
|
|
GND = J400.GND = pin 24/GND
|
||
|
|
|
||
|
|
Or you could flash firmware making the AVR into an SPI slave (keeping the
|
||
|
|
DataFlash in reset) and tweak the spi_butterfly driver to make it bind to
|
||
|
|
the driver for your custom SPI-based protocol.
|
||
|
|
|
||
|
|
The "USI" controller, using J405, can also be used for a second SPI bus.
|
||
|
|
That would let you talk to the AVR using custom SPI-with-USI firmware,
|
||
|
|
while letting either Linux or the AVR use the DataFlash. There are plenty
|
||
|
|
of spare parport pins to wire this one up, such as:
|
||
|
|
|
||
|
|
Signal Butterfly Parport (DB-25)
|
||
|
|
------ --------- ---------------
|
||
|
|
SCK = J403.PE4/USCK = pin 5/D3
|
||
|
|
MOSI = J403.PE5/DI = pin 6/D4
|
||
|
|
MISO = J403.PE6/DO = pin 12/S5,nPAPEROUT
|
||
|
|
GND = J403.GND = pin 22/GND
|
||
|
|
|
||
|
|
IRQ = J402.PF4 = pin 10/S6,ACK
|
||
|
|
GND = J402.GND(P2) = pin 25/GND
|
||
|
|
|